Work vehicle and method for controlling work vehicle

ABSTRACT

A work vehicle includes a vehicular body, a work implement, and a controller. The work implement has a boom pivotable with respect to the vehicular body, a dipper stick pivotable with respect to the boom, and a bucket pivotable with respect to the dipper stick. The controller calculates a direction of a cutting edge of the bucket and determines a direction in which the cutting edge travels to the side of an open side of the bucket such that the calculated direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle, and the controller thus causes an operation of the work implement to be performed in the direction in which the cutting edge travels.

TECHNICAL FIELD

The present invention relates to a work vehicle.

BACKGROUND ART

A work vehicle such as a hydraulic excavator comprises a work implementhaving a boom, a dipper stick, and a bucket. When the hydraulicexcavator starts an excavating operation, the dipper stick ismanipulated to cause the bucket to penetrate soil. As the bucketcontinues to operate, the bucket penetrates soil deeply and the soil'sresistance increases, and accordingly, the boom is manipulated to add anoperation to raise the bucket upward to make the bucket's excavationdepth appropriate. Furthermore, the dipper stick and the bucket aremanipulated and once sufficient soil is introduced into the bucket, thebucket is manipulated to lift up the soil, and furthermore, the boom ismanipulated to raise the bucket upward.

For a hydraulic excavator's excavating operation, it is necessary tomove manipulation levers of three-axes for the boom, the dipper stick,and the bucket, respectively, to manipulate the movement of the bucket,and it is thus not easy to perform the excavating operation efficientlyand requires skill.

In this respect, for example, Japanese Patent Laying-Open No. 61-225429discloses a method of correcting a bucket in posture by detecting acollision of a back surface of the bucket against an excavation surfacein order to reduce an excavation load.

Furthermore, Japanese Patent Laying-Open No. 62-189222 discloses amethod of adjusting a bucket's excavation depth by measuring the weightof the soil in the bucket.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laying-Open No. 61-225429

PTL 2: Japanese Patent Laying-Open No. 62-189222

SUMMARY OF INVENTION Technical Problem

However, the excavating operation in the above-mentioned publicationrequires various calculations and has a possibility of complicatedcontrol.

The present invention has been made in view of the above issue, and anobject of the present invention is to provide a work vehicle whichallows a work implement to operate efficiently in a simple manner, and amethod for controlling the work vehicle.

Solution to Problem

A work vehicle according to one aspect of the present inventioncomprises a vehicular body, a work implement, and a controller. The workimplement has a boom pivotable with respect to the vehicular body, adipper stick pivotable with respect to the boom, and a bucket pivotablewith respect to the dipper stick. The controller calculates a directionof a cutting edge of the bucket and determines a direction in which thecutting edge travels to the side of an open side of the bucket such thatthe calculated direction of the cutting edge of the bucket and thedirection in which the cutting edge travels to the side on the open sideof the bucket form an excavation angle of a predetermined angle, and thecontroller causes an operation of the work implement to be performed inthe direction in which the cutting edge travels.

Preferably, the controller determines the direction in which the cuttingedge travels to the side on the open side of the bucket such that thecalculated direction of the cutting edge of the bucket and the directionin which the cutting edge travels to the side on the open side of thebucket form the excavation angle of the predetermined angle for apredetermined period of time, and the controller causes the operation ofthe work implement to be performed in the direction in which the cuttingedge travels.

Preferably, the work vehicle further comprises first and secondmanipulation levers. The first manipulation lever is operated to outputa first manipulation command to the controller to adjust an amount ofpivoting the bucket with respect to the dipper stick. The secondmanipulation lever is operated to output a second manipulation commandto the controller to adjust an amount of moving the bucket for thedirection in which the cutting edge travels from the direction of thecutting edge to the side on the open side of the bucket.

Preferably, the controller determines whether to cause the operation ofthe work implement to be performed. When the controller determines thatthe operation of the work implement is caused to be performed, thecontroller accepts first and second manipulation commands from the firstand second manipulation levers.

Preferably, the controller determines whether to cause the operation ofthe work implement to be performed in accordance with a manipulationinstruction of an operator.

Preferably, the work vehicle further comprises a load detector. The loaddetector detects a load imposed on the work implement. The controllerdetermines whether to cause the operation of the work implement to beperformed according to a result of detection by the load detector.

According to one aspect of the present invention, a method forcontrolling a work vehicle is a method for controlling a work vehicleincluding a work implement having a boom pivotable with respect to avehicular body, a dipper stick pivotable with respect to the boom, and abucket pivotable with respect to the dipper stick, comprising:calculating a direction of a cutting edge of the bucket; and causing anoperation of the work implement to be performed such that the directionof the cutting edge of the bucket as calculated and the direction inwhich the cutting edge travels to the side on the open side of thebucket form an excavation angle of a predetermined angle.

Advantageous Effects of Invention

The present work vehicle allows a work implement to operate efficientlyin a simple manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of one example of a work vehicle accordingto an embodiment.

FIG. 2 schematically illustrates a work vehicle CM according to anembodiment.

FIG. 3 is a functional block diagram representing a configuration of acontrol system 200 to control work vehicle CM according to anembodiment.

FIG. 4 represents a relationship between an excavation angle of a bucket8 and resistance of soil according to an embodiment.

FIG. 5 is a flowchart of a process of an operation of an excavation workof work vehicle CM according to an embodiment.

FIG. 6 is a functional block diagram representing a configuration of acontrol system 200# based on a first modification of an embodiment.

FIG. 7 represents an idea of a work vehicle system based on anotherembodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings, although the present invention is notlimited thereto. Any constituent element of each embodiment describedbelow can be combined as appropriate. Some constituent element may notbe used.

[General Configuration of Work Vehicle]

FIG. 1 is a perspective view of one example of a work vehicle accordingto an embodiment.

As shown in FIG. 1, in the present example, a work vehicle will bedescribed by referring as an example to a hydraulic excavator CMincluding a hydraulically actuated work implement 2 as a work implement.

Hydraulic excavator CM includes a vehicular body 1 and work implement 2.

Vehicular body 1 has a revolving unit 3, an operator's cab 4, and atravelling unit 5.

Revolving unit 3 is disposed on a travelling unit 5. Travelling unit 5supports revolving unit 3. Revolving unit 3 can revolve about an axisAX. An operator's seat 4S on which an operator is seated is provided inoperator's cab 4. The operator manipulates hydraulic excavator CM inoperator's cab 4. Travelling unit 5 has a pair of crawler belts 5Cr.Hydraulic excavator CM travels as crawler belts 5Cr rotate. Note thattravelling unit 5 may be composed of vehicular wheels (or tires).

In the present embodiment, a positional relationship of each part willbe described with reference to an operator seated on operator's seat 4Sin the cab.

A frontward/rearward direction is a frontward/rearward direction withreference to the operator seated on operator's seat 4S. Arightward/leftward direction is a rightward/leftward direction withrespect to the operator seated on operator's seat 4S. Therightward/leftward direction matches the vehicle's widthwise direction(a vehicular widthwise direction). When the operator is seated onoperator's seat 4S and faces frontward, the operator faces in thefrontward direction, and a direction opposite to the frontward directionis the rearward direction. When the operator is seated on operator'sseat 4S and faces frontward, a direction on a right side of the operatoris referred to as the rightward direction, and a direction on a leftside of the operator is referred to as the leftward direction. Thefrontward/rearward direction is a direction along the x axis and therightward/leftward direction is a direction along the y axis. When theoperator is seated on operator's seat 4S and faces frontward, theoperator faces in the frontward direction (or a +x direction), and adirection opposite to the frontward direction is the rearward direction(or a −x direction). When the operator is seated on operator's seat 4Sand faces frontward, a direction on one side of the operator in thevehicular widthwise direction is the right direction (or a +zdirection), and a direction on the other side of the operator in thevehicular widthwise direction is the left direction (or a −z direction).

Revolving unit 3 has an engine compartment 9 in which an engine ishoused, and a counter weight provided at a rear portion of revolvingunit 3. Revolving unit 3 is provided with a handrail 19 in front ofengine compartment 9. The engine, a hydraulic pump, etc. are disposed inengine compartment 9.

Work implement 2 is connected to revolving unit 3.

Work implement 2 has a boom 6, a dipper stick 7, a bucket 8, a boomcylinder 10, a dipper stick cylinder 11, and a bucket cylinder 12.

Boom 6 is connected to revolving unit 3 via a boom pin 13. Dipper stick7 is connected to boom 6 via a dipper stick pin 14. Bucket 8 isconnected to dipper stick 7 via a bucket pin 15. Boom cylinder 10 drivesboom 6. Dipper stick cylinder 11 drives dipper stick 7. Bucket cylinder12 drives bucket 8. Boom 6 has a proximal end (or a boom foot) connectedto revolving unit 3. Boom 6 has a distal end (or a boom top) connectedto a proximal end of dipper stick 7. Dipper stick 7 has a distal end (ora dipper stick top) connected to a proximal end of bucket 8. Boomcylinder 10, dipper stick cylinder 11, and bucket cylinder 12 are all ahydraulic cylinder driven with hydraulic oil.

Boom 6 is pivotable with respect to revolving unit 3 about boom pin 13serving as a pivot. Dipper stick 7 is pivotable with respect to boom 6about dipper stick pin 14 serving as a pivot parallel to boom pin 13.Bucket 8 is pivotable with respect to dipper stick 7 about bucket pin 15serving as a pivot parallel to boom pin 13 and dipper stick pin 14.

Boom pin 13, dipper stick pin 14, and bucket pin 15 are all parallel tothe z axis. Boom 6, dipper stick 7, and bucket 8 are all pivotable aboutan axis parallel to the z axis.

FIG. 2 schematically illustrates work vehicle CM according to anembodiment.

As shown in FIG. 2, work vehicle CM is provided with a boom cylinderstroke sensor 16, a dipper stick cylinder stroke sensor 17, and a bucketcylinder stroke sensor 18.

Boom cylinder stroke sensor 16 is disposed on boom cylinder 10 andsenses a length of a stroke of boom cylinder 10 (a boom cylinderlength). Dipper stick cylinder stroke sensor 17 is disposed on dipperstick cylinder 11 and senses a length of a stroke of dipper stickcylinder 11 (a dipper stick cylinder length). Bucket cylinder strokesensor 18 is disposed on bucket cylinder 12 and senses a length of astroke of bucket cylinder 12 (bucket cylinder length).

In the following description, a length of a stroke of boom cylinder 10will also be referred to as a boom cylinder length or a boom stroke. Alength of a stroke of a dipper stick cylinder 11 will also be referredto as a dipper stick cylinder length or a dipper stick stroke. A lengthof a stroke of bucket cylinder 12 will also be referred to as a bucketcylinder length or a bucket stroke.

Furthermore, the boom cylinder length, the dipper stick cylinder lengthand the bucket cylinder length will collectively be also referred to ascylinder length data.

Boom 6 has a length L1, which is a distance between boom pin 13 anddipper stick pin 14. Dipper stick 7 has a length L2, which is a distancebetween dipper stick pin 14 and bucket pin 15. Bucket 8 has a length L3,which is a distance between bucket pin 15 and a cutting edge 8 a ofbucket 8. Bucket 8 has a plurality of blades, and in the presentexample, a tip portion of bucket 8 will be referred to as cutting edge 8a. Note that bucket 8 may have no blade. The tip portion of bucket 8 maybe formed of a steel plate having a straight shape.

In the present example, an x- and y-axis vehicular body coordinatesystem with boom pin 13 as a reference point (or a reference position)is shown.

An inclination angle θ1 of boom 6 with respect to a horizontal directionin the vehicular body coordinate system is calculated from cylinderlength data sensed by boom cylinder stroke sensor 16.

An inclination angle θ2 of dipper stick 7 with respect to boom 6 iscalculated from cylinder length data sensed by dipper stick cylinderstroke sensor 17.

An inclination angle θ3 of cutting edge 8 a of bucket 8 with respect todipper stick 7 is calculated from cylinder length data sensed by bucketcylinder stroke sensor 18.

Based on lengths L1 to L3 and inclination angles θ1 to θ3 of boom 6,dipper stick 7 and bucket 8, a position of cutting edge 8 a of bucket 8and an angle of cutting edge 8 a of bucket 8 (the cutting edge'sdirection) in the x- and y-axis vehicular body coordinate system can becalculated.

In the present example, positional coordinates [x1, y1] of cutting edge8 a of bucket 8 and a cutting edge angle [a] of cutting edge 8 a ofbucket 8 with respect to the horizontal direction are shown.

While in the present example a method of sensing a stroke length byusing a stroke sensor, and calculating inclination angle θ will bedescribed, the inclination angle may be calculated by using an angledetector such as a rotary encoder.

[Configuration of Hydraulic System]

FIG. 3 is a functional block diagram representing a configuration of acontrol system 200 to control work vehicle CM according to anembodiment.

As shown in FIG. 3, control system 200 according to the embodimentcontrols an excavation process using work implement 2.

Control system 200 includes boom cylinder stroke sensor 16, dipper stickcylinder stroke sensor 17, bucket cylinder stroke sensor 18, amanipulation device 25, a work implement controller 26, a hydrauliccylinder 60, a directional control valve 64, and a pressure sensor 66.

Manipulation device 25 is disposed in operator's cab 4. Manipulationdevice 25 is manipulated by the operator. Manipulation device 25receives a manipulation command of the operator to drive work implement2. Manipulation device 25 is a manipulation device of a pilot hydraulicsystem as an example.

Directional control valve 64 adjusts an amount of hydraulic oil suppliedto hydraulic cylinder 60. Directional control valve 64 is actuated byoil supplied. In the present example, oil supplied to a hydrauliccylinder (boom cylinder 10, dipper stick cylinder 11, and bucketcylinder 12) in order to actuate the hydraulic cylinder is also referredto as hydraulic oil. Furthermore, oil supplied to directional controlvalve 64 to actuate directional control valve 64 is referred to as pilotoil. Furthermore, the pilot oil's pressure is also referred to as pilotoil pressure.

The hydraulic oil and the pilot oil may be pumped from the samehydraulic pump. For example, the hydraulic oil pumped from the hydraulicpump may have a portion reduced in pressure by a reducing valve, and thehydraulic oil reduced in pressure may be used as the pilot oil. Further,a hydraulic pump (a main hydraulic pump) for pumping the hydraulic oiland a hydraulic pump (a pilot hydraulic pump) for pumping the pilot oilmay be different hydraulic pumps.

Further, in the present example, the pilot oil pumped from the mainhydraulic pump and reduced in pressure by the reducing valve is suppliedto manipulation device 25.

The pilot oil pressure is adjusted based on the amount of manipulatingmanipulation device 25. Pressure sensor 66 is connected to manipulationdevice 25. Pressure sensor 66 senses a pilot oil pressure generated inresponse to manipulation of a lever of manipulation device 25 andoutputs it to work implement controller 26.

In response to the pilot oil pressure sensed by pressure sensor 66, workimplement controller 26 drives directional control valve 64 passing thehydraulic oil supplied to hydraulic cylinder 60 (boom cylinder 10,dipper stick cylinder 11, and bucket cylinder 12).

Manipulation device 25 includes a first manipulation lever 25R, a secondmanipulation lever 25L, and an excavation mode setting button 25P. Firstmanipulation lever 25R is disposed, for example, on the right side ofdriver's seat 4S. Second manipulation lever 25L is disposed, forexample, on the left side of operator's seat 4S. For first manipulationlever 25R and second manipulation lever 25L, forward, backward,rightward and leftward operations correspond to operations along twoaxes.

Excavation mode setting button 25P is a setting button for setting anexcavation mode. Work implement controller 26 shifts from a normal modeto the excavation mode in response to an instruction issued as theoperator presses excavation mode setting button 25P. Furthermore, workimplement controller 26 shifts from the excavation mode to the normalmode in response to an instruction issued as the operator again pressesexcavation mode setting button 25P.

In the present example, first manipulation lever 25R and secondmanipulation lever 25L of manipulation device 25 can change a functioncorresponding to a manipulation between the normal mode and theexcavation mode.

In the normal mode, first manipulation lever 25R is manipulated tomanipulate boom 6 and bucket 8.

A forward/backward manipulation of first manipulation lever 25Rcorresponds to a manipulation of boom 6, and in response to theforward/backward manipulation, boom 6 is raised/lowered. The lever ismanipulated to manipulate boom 6.

A rightward/leftward manipulation of first manipulation lever 25Rcorresponds to a manipulation of bucket 8, and in response to therightward/leftward manipulation, bucket 8 is operated to excavate soiland be released. The lever is manipulated to manipulate bucket 8.

Second manipulation lever 25L is manipulated to manipulate dipper stick7 and revolving unit 3.

A forward/backward manipulation of second manipulation lever 25Lcorresponds to a manipulation of dipper stick 7, and in response to theforward/backward manipulation, dipper stick 7 is raised/lowered. Thelever is manipulated to manipulate dipper stick 7.

A rightward/leftward manipulation of second manipulation lever 25Lcorresponds to revolution of revolving unit 3, and in response to therightward/leftward manipulation, revolving unit 3 revolves rightward andleftward.

In response to an amount of manipulating first manipulation lever 25R inthe forward/backward direction (an amount of manipulating the boom), asbased on a result of detection by pressure sensor 66, work implementcontroller 26 drives directional control valve 64 passing hydraulic oilsupplied to boom cylinder 10 for driving boom 6.

In response to an amount of manipulating first manipulation lever 25R inthe rightward and leftward direction (an amount of manipulating thebucket), as based on a result of detection by pressure sensor 66, workimplement controller 26 drives directional control valve 64 passinghydraulic oil supplied to bucket cylinder 12 for driving bucket 8.

In response to an amount of manipulating second manipulation lever 25Lin the forward/backward direction (an amount of manipulating the dipperstick), as based on a result of detection by pressure sensor 66, workimplement controller 26 drives directional control valve 64 passinghydraulic oil supplied to dipper stick cylinder 11 for driving dipperstick 7.

In response to an amount of manipulating second manipulation lever 25Lin the rightward and leftward direction, as based on a result ofdetection by pressure sensor 66, work implement controller 26 drivesdirectional control valve 64 passing hydraulic oil supplied to ahydraulic actuator for driving revolving unit 3.

Note that a rightward/leftward manipulation of first manipulation lever25R may correspond to a manipulation of boom 6 and a forward/backwardmanipulation thereof may correspond to that of bucket 8. Note that arightward/leftward manipulation of second manipulation lever 25L maycorrespond to a manipulation of dipper stick 7 and a forward/backwardmanipulation thereof may correspond to that of revolving unit 3.

In the excavation mode, first manipulation lever 25R is manipulated tomanipulate bucket 8. A rightward/leftward manipulation of firstmanipulation lever 25R corresponds to a manipulation of bucket 8, and inresponse to the rightward/leftward manipulation, bucket 8 is rotated.The forward/backward manipulation of first manipulation lever 25R isdisabled. Accordingly, no manipulation of the lever to manipulate boom 6is accepted.

In the excavation mode, second manipulation lever 25L is manipulated toadjust an amount of moving cutting edge 8 a of bucket 8. Forwardmanipulation of second manipulation lever 25L corresponds to controllingan amount of moving cutting edge 8 a of bucket 8. When secondmanipulation lever 25L is inclined forward in a large amount bucket 8has cutting edge 8 a moved in an increased amount. When secondmanipulation lever 25L is inclined forward in a small amount bucket 8has cutting edge 8 a moved in a reduced amount.

Manipulation of second manipulation lever 25L in any other direction isdisabled. Accordingly, no manipulation of the lever to manipulate dipperstick 7 and revolving unit 3 is accepted.

[Resistance of Soil]

FIG. 4 represents a relationship between an excavation angle of bucket 8and resistance of soil according to an embodiment.

In the present example, an excavation angle represents an angle betweena direction of cutting edge 8 a of bucket 8 and a direction in whichcutting edge 8 a travels when bucket 8 moves. With reference to thedirection of cutting edge 8 a of bucket 8, when bucket 8 moves andcutting edge 8 a travels in a direction to a side on the open side ofbucket 8, the angle has a positive value, whereas when the cutting edgetravels in the opposite direction, the angle has a negative value.

As shown in FIG. 4, an excavation angle of bucket 8 around 0° isindicated as a limit angle.

When bucket 8 has an excavation angle smaller than the limit angle,bucket 8 has its exterior or back surface pressed against soil, whichrapidly increases a value of resistance of soil against bucket 8.

On the other hand, the figure shows that when bucket 8 has an excavationangle of a predetermined angle Q, bucket 8 experiences resistance ofsoil of a minimum value against it.

It should be noted that the limit angle and the predetermined angle Qare merely examples and can be set to different values depending on theform of bucket 8.

Work vehicle CM according to the present embodiment performs anexcavation process at an excavation angle with a small value ofresistance of soil to operate a work implement in a simple mannerefficiently. Specifically, work vehicle CM performs the excavationprocess such that the excavation angle is the predetermined angle Q.Note that in the present example, being the predetermined angle Q doesnot necessarily mean completely matching the predetermined angle Q, andalso includes a value approximate to the predetermined angle Q.

[Process of Operation]

FIG. 5 is a flowchart of a process of an operation of an excavation workof work vehicle CM according to an embodiment.

As shown in FIG. 5, work implement controller 26 determines whether theexcavation mode is set (step S2). Specifically, work implementcontroller 26 determines whether a setting instruction via theexcavation mode setting button to set the excavation mode in response toa manipulation command of the operator is received.

In step S2, if work implement controller 26 determines that theexcavation mode is set, work implement controller 26 calculates cuttingedge data (step S4).

Specifically, work implement controller 26 calculates a boom cylinderlength, a dipper stick cylinder length, and a bucket cylinder lengthbased on detection results obtained from boom cylinder stroke sensor 16,dipper stick cylinder stroke sensor 17, and bucket cylinder strokesensor 18. Inclination angle θ1 of boom 6 with respect to the horizontaldirection is calculated from the boom cylinder length. Inclination angleθ2 of dipper stick 7 with respect to boom 6 is calculated from thedipper stick cylinder length. Inclination angle θ3 of cutting edge 8 aof bucket 8 with respect to dipper stick 7 is calculated from the bucketcylinder length. Thus, cutting edge data [x1, y1, α1] indicating aposition of bucket 8 and a direction of cutting edge 8 a of bucket 8(the cutting edge's direction) in the x- and y-axis vehicular bodycoordinate system is calculated.

Subsequently, work implement controller 26 calculates an excavatingdirection vector (step S6).

In the present example, the excavating direction vector is calculatedsuch that an excavation angle formed between a direction in whichcutting edge 8 a of bucket 8 travels with respect to a direction ofcutting edge 8 a of bucket 8 is the predetermined angle Q. Thus, adirection in which cutting edge 8 a of bucket 8 travels to a side on theopen side of bucket 8 is determined.

The excavating direction vector in the vehicular body coordinate systemof the present example is indicated by unit vectors dx and dy along thex axis and the y axis, which are represented by the followingexpressions:

dx=−cos(α1+Q)

dy=−sin(α1+Q).

Subsequently, work implement controller 26 accepts an input via amanipulation lever (step S8).

In the present example, manipulation inputs via first manipulation lever25R and second manipulation lever 25L are accepted.

As has been described above, in the excavation mode, first manipulationlever 25R is manipulated to rotate bucket 8. Second manipulation lever25L is manipulated to move the bucket for an excavating direction.

Subsequently, work implement controller 26 calculates an amount ofpivoting the bucket and an amount of moving the bucket for excavation inaccordance with manipulation inputs received via the manipulation levers(step S10).

Specifically, work implement controller 26 calculates the amount ofrotating the bucket based on a pressure generated in response to themanipulation input via first manipulation lever 25R and sensed by andoutput from pressure sensor 66. Furthermore, work implement controller26 calculates the amount of moving the bucket for excavation based on apressure generated in response to the manipulation input via secondmanipulation lever 25L and sensed by and output from pressure sensor 66.

In the present example, the amount of rotating the bucket and the amountof moving the bucket for excavation based on a result of calculationdone by work implement controller 26 are represented as Δd and Δe,respectively.

Subsequently, work implement controller 26 calculates target cuttingedge data for cutting edge 8 a of bucket 8 moving in response to aninput via a manipulation lever (step S12).

Specifically, work implement controller 26 calculates target cuttingedge data [x2, y2, α2].

x2=x1+Δd×dx

y2=y1+Δd×dy

α2=α1+Δe

The target cutting edge data [x2, y2, α2] can be calculated from theabove equations.

Subsequently, work implement controller 26 operates the work implementbased on the target cutting edge data (step S14)

Specifically, work implement controller 26 calculates an inclinationangle θ1′ of boom 6, an inclination angle θ2′ of dipper stick 7, and aninclination angle θ3′ of bucket 8 in accordance with the target cuttingedge data [x2, y2, α2] of cutting edge 8 a of bucket 8 in the x- andy-axis vehicular body coordinate system. Work implement controller 26calculates a boom cylinder length, a dipper stick cylinder length and abucket cylinder length based on inclination angles θ1′ to θ3′ of boom 6,dipper stick 7 and bucket 8.

Then, work implement controller 26 drives directional control valve 64so as to adjust hydraulic oil supplied to hydraulic cylinder 60 so as toachieve the calculated boom, dipper stick and bucket cylinder lengths.

Thus, boom 6, dipper stick 7 and bucket 8 are automatically controlledso that cutting edge 8 a of bucket 8 has a position and a direction asindicated by the target cutting edge data.

Subsequently, work implement controller 26 determines whether a work hasended (step S16). When work implement controller 26 determines that thework has ended is for example when the engine is stopped.

In step S16, if work implement controller 26 determines that the workhas ended (YES in step S16), work implement controller 26 ends theprocess (END).

On the other hand, if work implement controller 26 determines in stepS16 that the work has not ended (NO in step S16), work implementcontroller 26 returns to step S2 and repeats the above process.

On the other hand, if work implement controller 26 determines in step S2that the excavation mode is not set, work implement controller 26accepts an input via a manipulation lever (step S18).

In the present example, manipulation inputs via first manipulation lever25R and second manipulation lever 25L are accepted.

As has been previously discussed, in the normal mode, first manipulationlever 25R is manipulated to manipulate boom 6 and bucket 8. Furthermore,second manipulation lever 25L is manipulated to manipulate dipper stick7 and revolving unit 3.

And work implement controller 26 operates the work implement (step S20).

In response to an amount of manipulating first manipulation lever 25R inthe forward/backward direction (an amount of manipulating the boom), asbased on a result of detection by pressure sensor 66, work implementcontroller 26 drives directional control valve 64 passing hydraulic oilsupplied to boom cylinder 10 for driving boom 6.

In response to an amount of manipulating first manipulation lever 25R inthe rightward and leftward direction (an amount of manipulating thebucket), as based on a result of detection by pressure sensor 66, workimplement controller 26 drives directional control valve 64 passinghydraulic oil supplied to bucket cylinder 12 for driving bucket 8.

In response to an amount of manipulating second manipulation lever 25Lin the forward/backward direction (an amount of manipulating the dipperstick), as based on a result of detection by pressure sensor 66, workimplement controller 26 drives directional control valve 64 passinghydraulic oil supplied to dipper stick cylinder 11 for driving dipperstick 7.

In response to an amount of manipulating second manipulation lever 25Lin the rightward and leftward direction, as based on a result ofdetection by pressure sensor 66, work implement controller 26 drivesdirectional control valve 64 passing hydraulic oil supplied to thehydraulic actuator for driving revolving unit 3.

Subsequently, the control proceeds to step S16.

The process subsequent to the step is similar to that described above,and accordingly, will not be described repeatedly in detail.

In the present example, a direction of cutting edge 8 a of bucket 8 iscalculated, and an excavating direction vector (a direction in whichcutting edge 8 a of bucket 8 travels to a side on the open side ofbucket 8) is calculated such that an excavation angle formed between thedirection in which cutting edge 8 a of bucket 8 travels with respect tothe direction of cutting edge 8 a of bucket 8 is the predetermined angleQ. Automatic control is done to move cutting edge 8 a of bucket 8 inaccordance with the excavating direction vector, and resistance of soilagainst bucket 8 is reduced. Reduced resistance (or load) of soilagainst bucket 8 allows the work implement to operate efficiently in asimple manner.

Further, in the present example, while an excavation mode is set inaccordance with an instruction issued as an operator presses excavationmode setting button 25P, the work implement is operated efficiently witha small load as cutting edge 8 a of bucket 8 moves in accordance with apredetermined excavating direction vector, and improved fuel economy canbe achieved.

Further, in the present example, the excavation mode can be set inresponse to an instruction issued as an operator presses excavation modesetting button 25P, and the work implement can be operated efficientlywith the operator's intention reflected.

Further, in the present example, in the excavation mode, firstmanipulation lever 25R is manipulated to rotate bucket 8. Further,second manipulation lever 25L is manipulated to move the bucket for anexcavating direction. Thus an excavation process is performed inresponse to manipulation commands via two manipulation levers.

For a conventional hydraulic excavator's excavating operation it isnecessary to move manipulation levers of three axes for a boom, a dipperstick, and a bucket, respectively, to manipulate the movement of thebucket, so that it is not easy and requires skill, whereas the presentsystem of the present example allows the movement of the bucket to bemanipulated by two manipulation commands so that an efficient excavationprocess can be performed through a simple manipulation.

First Modification

A work vehicle according to a first modification of the embodiment isnot limited to being controlled by an operator's manipulationinstruction, and may autonomously control work vehicle CM in theexcavation mode.

Specifically, work implement controller 26 determines whether workimplement 2 performs an excavation work.

In the first modification will be described a case where whether workimplement 2 performs an excavation work is determined depending on aload imposed on work implement 2.

FIG. 6 is a functional block diagram representing a configuration of acontrol system 200# based on the first modification of an embodiment.

As shown in FIG. 6, control system 200# differs from control system 200in that a load sensor 28 is further provided. Furthermore, the formerdiffers from the latter in that manipulation device 25 is replaced by amanipulation device 25 #.

Compared to manipulation device 25, manipulation device 25# shows aconfiguration excluding excavation mode setting button 25P. Theremainder in configuration is similar to that described with referenceto FIG. 3, and accordingly, it will not be described repeatedly indetail.

In the present example, it is assumed that load sensor 28 is attached tobucket 8 as an example.

Work implement controller 26 determines whether work implement 2performs an excavation work in accordance with load sensor 28 attachedto bucket 8.

When bucket 8 excavates soil, i.e., when bucket 8 is engaged in anexcavation work, load sensor 28 indicates an increased value. Whenbucket 8 does not excavate soil, i.e., when the bucket 8 is not engagedin an excavation work, load sensor 28 indicates a reduced value.

In the present example, work implement controller 26 determines whethera value of a load according to a result of detection from load sensor 28is a predetermined value or more.

When work implement controller 26 determines that a value of a loadaccording to a result of detection from load sensor 28 is thepredetermined value or more, work implement controller 26 determinesthat the excavation work is performed, and sets the excavation mode.

When work implement controller 26 sets the excavation mode, and firstmanipulation lever 25R is manipulated, bucket 8 is rotated. Further,when second manipulation lever 25L is manipulated the bucket is movedfor an excavating direction. Thus an excavation process is performed inresponse to two manipulation commands.

On the other hand, when a value of a load according to a result ofdetection from load sensor 28 is less than the predetermined value, workimplement controller 26 does not set the excavation mode. In that case,work implement controller 26 operates in the normal mode.

When work implement controller 26 sets the normal mode, and firstmanipulation lever 25R is manipulated, boom 6 and bucket 8 aremanipulated. Furthermore, when second manipulation lever 25L ismanipulated, dipper stick 7 and revolving unit 3 are manipulated.

The work vehicle according to the first modification of the embodimentis of a system to autonomously control work vehicle CM in the excavationmode in accordance with a result of detection from load sensor 28.

This allows the work implement to be operated efficiently in a simplemanner.

While in the present embodiment a configuration has been described inwhich load sensor 28 is attached to bucket 8, it is also possible toadopt a configuration in which a load is sensed by a sensor thatmeasures oil pressure in the hydraulic cylinder. For example, the oilpressure of the hydraulic oil supplied to bucket cylinder 12 may bemeasured with a sensor to determine a load imposed on bucket 8 inmagnitude.

While in the excavation mode, in the above description, a method ofmanipulating bucket 8 in accordance with manipulation instructions of anoperator via first manipulation lever 25R and second manipulation lever25L in step S8 has been described, this is not exclusive, and bucket 8may be automatically controlled. More specifically, work implementcontroller 26 may automatically control bucket 8 by setting an amount ofrotating the bucket and an amount of moving the bucket for excavation toa previously programmed and thus set, predetermined value. Thepredetermined value is not limited to a fixed value. For example, thepredetermined value may be changed as time elapses after the excavationmode is started. For example, for a predetermined period of time afterthe excavation mode is started, i.e., while an excavation process isperformed to introduce soil into bucket 8, the predetermined value maybe set to a first predetermined value, whereas while the excavationprocess is performed to scrape soil out of bucket 8, the predeterminedvalue may be set to a second predetermined value.

Other Embodiment

FIG. 7 is a diagram for illustrating an idea of a work vehicle systembased on another embodiment.

As shown in FIG. 7, the work vehicle system according to the otherembodiment configures a control system to control work vehicle CM froman external base station 300. More specifically, it is a configurationin which a function of work implement controller 26 and manipulationdevice 25 described in FIG. 3 is provided in external base station 300or the like.

Base station 300 includes a work implement controller 26# similar infunction to work implement controller 26 and a manipulation device 25#similar in function to manipulation device 25.

Work implement controller 26# receives a manipulation command viamanipulation device 25# and outputs an operation command for controllingwork vehicle CM. Work vehicle CM operates in response to the operationcommand issued from work implement controller 26#. More specifically,work implement controller 26# outputs an operation command for drivingdirectional control valve 64 described in FIG. 3. Further, workimplement controller 26# receives information from boom cylinder strokesensor 16, dipper stick cylinder stroke sensor 17 and bucket cylinderstroke sensor 18.

This configuration also allows the process for the operation of theexcavation work described in the first embodiment with reference to FIG.5 to be performed by work implement controller 26#.

Thus, even when the work vehicle is controlled from the remote basestation 300, the configuration in accordance with the present embodimentcan be applied to perform an efficient excavation work.

While in the present embodiment a configuration is described in which anoperator controls work vehicle CM in accordance with a manipulationinput via a manipulation lever which is a manipulation device, thepresent invention is also applicable to a configuration in which themanipulation device is not provided and work vehicle CM is autonomouslycontrolled. For example, the present invention can also be applied to acase where a manipulation command to perform an excavation work ispreprogrammed and the work implement controller operates in response tothe programmed manipulation command. Specifically, it suffices toinclude a process in which when an autonomous control program forautonomously controlling work vehicle CM is started in accordance with auser's instruction and the work implement controller operates inresponse to the programmed manipulation command, a direction of thecutting edge of the bucket is calculated and a direction in which thecutting edge travels from the cutting edge's direction to a side on theopen side of the bucket is determined such that the direction of thecutting edge of the bucket and the direction in which the cutting edgetravels to the side on the open side of the bucket form an excavationangle of a predetermined angle, and the work implement is operatedaccordingly.

Furthermore, while in the above description a case where a predeterminedangle Q for which resistance of soil has a minimal value is used hasbeen described, this is not exclusive, and work implement 2 may becontrolled with any predetermined angle set as the excavation angle. Thevalue of the excavation angle is not limited to a fixed value, either.For example, the value of the excavation angle may be changed as timeelapses after the excavation mode is started. For example, for apredetermined period of time after the excavation mode is started, i.e.,while an excavation process is performed to introduce soil into bucket8, the excavation angle may be set to a first excavation angle, whereaswhile the excavation process is performed to scrape soil out of bucket8, the excavation angle may be set to a second excavation angle.

<Function and Effect>

A function and effect of the present embodiment will be described.

According to the present embodiment, work vehicle CM includes vehicularbody 1 and work implement 2, as shown in FIG. 1 Work implement 2 hasboom 6 pivotable with respect to vehicular body 1, dipper stick 7pivotable with respect to boom 6, and bucket 8 pivotable with respect todipper stick 7. As shown in FIG. 3, work vehicle CM is provided withwork implement controller 26. Work implement controller 26 calculates adirection of cutting edge 8 a of bucket 8 and determines an excavatingdirection vector (a direction in which cutting edge 8 a travels to aside on the open side of bucket 8) such that the direction of cuttingedge 8 a of bucket 8 and the direction in which cutting edge 8 a travelsto the side on the open side of bucket 8 form an excavation angle of apredetermined angle Q, and work implement controller 26 causes anoperation of the work implement to be performed in the direction inwhich the cutting edge travels.

As shown in FIG. 4, causing work implement 2 to perform an excavationprocess at the excavation angle of the predetermined angle Q for whichresistance of soil has a minimal value allows the work implement tooperate efficiently in a simple manner.

Work implement controller 26 determines an excavating direction vectorsuch that the calculated direction of cutting edge 8 a of bucket 8 andthe direction in which cutting edge 8 a travels to the side on the openside of bucket 8 form an excavation angle of the predetermined angle Qfor a predetermined period of time, and work implement controller 26causes an operation of the work implement to be performed in thedirection in which the cutting edge travels.

As shown in FIG. 4, performing an excavation process at an excavationangle with a small value of resistance of soil for a predeterminedperiod of time allows the work implement to operate efficiently and fueleconomy to be improved.

Work vehicle CM is provided with first manipulation lever 25R operatedto output a first manipulation command to work implement controller 26to adjust an amount of pivoting bucket 8 with respect to dipper stick 7and second manipulation lever 25L operated to output a secondmanipulation command to work implement controller 26 to adjust an amountof moving bucket 8 for a direction in which cutting edge 8 a travels tothe side on the open side of bucket 8 from the direction of cutting edge8 a.

As an excavation process is performed in response to manipulationcommands via two manipulation levers, the excavation process can beperformed more efficiently through a simpler manipulation than aconventional hydraulic excavator's excavating operation in whichmanipulation levers of three axes for a boom, a dipper stick, and abucket, respectively, are moved to manipulate the movement of thebucket.

Work implement controller 26 determines whether the current mode is anexcavation mode in which work implement 2 performs an operation thereofwhich is an excavation work. When work implement controller 26determines that the current mode is the excavation mode in which workimplement 2 performs an excavation work, work implement controller 26accepts first and second manipulation commands via first manipulationlever 25R and second manipulation lever 25L.

When work implement controller 26 determines that the current mode isthe excavation mode, work implement controller 26 accepts first andsecond manipulation commands via two manipulation levers to manipulatebucket 8, and the excavation process can be performed efficiently.

Work implement controller 26 determines, according to an instructionissued as the operator presses excavation mode setting button 25P,whether the current mode is an excavation mode in which work implement 2performs an operation thereof which is an excavation work.

Whether the current mode is the excavation mode can be determinedaccording to an instruction issued as the operator presses excavationmode setting button 25P, and the work implement can be operatedefficiently with the operator's intention reflected.

Work vehicle CM is provided with load sensor 28 to sense a load imposedon bucket 8. Work implement controller 26 determines according to aresult of detection by load sensor 28 whether the current mode is aworking mode in which work implement 2 performs an operation thereofwhich is an excavation work.

As whether the current mode is the working mode can be determinedaccording to a result of detection by load sensor 28, the operator'smanipulation instruction is unnecessary, and the work implement can beoperated efficiently in a simple manner.

According to the present embodiment, work vehicle CM includes vehicularbody 1 and work implement 2, as shown in FIG. 1. Work implement 2 hasboom 6 pivotable with respect to vehicular body 1, dipper stick 7pivotable with respect to boom 6, and bucket 8 pivotable with respect todipper stick 7. A method for controlling work vehicle CM comprises thesteps of: calculating a direction of cutting edge 8 a of bucket 8; andcausing an operation of a work implement to be performed in a directionin which cutting edge 8 a travels to a side on the open side of bucket 8such that the calculated direction of cutting edge 8 a of bucket 8 andthe direction in which cutting edge 8 a travels to the side on the openside of bucket 8 form an excavation angle of a predetermined angle Q.

As shown in FIG. 4, it is possible to cause work implement 2 to performan excavation process at the excavation angle of the predetermined angleQ for which resistance of soil has a minimal value, and it is possibleto operate the work implement efficiently in a simple manner.

While a hydraulic excavator has been described as a work vehicle in thepresent example, the work vehicle is also applicable to a crawler dozer,a wheel loader and other similar work vehicles.

While the present invention has been described in embodiments, it shouldbe understood that the embodiments disclosed herein are illustrative andnon-restrictive in any respect. The scope of the present invention isdefined by the terms of the claims, and is intended to include anymodifications within the meaning and scope equivalent to the terms ofthe claims.

REFERENCE SIGNS LIST

1 vehicular body, 2 work implement, 3 revolving unit, 4 operator's cab,4 s operator's seat, 5 traveling unit, 5Cr crawler, 6 boom, 7 dipperstick, 8 bucket, 8 a cutting edge, 9 engine room, 10 boom cylinder, 11dipper stick cylinder, 12 bucket cylinder, 13 boom pin, 14 dipper stickpin, 15 bucket pin, 16 boom cylinder stroke sensor, 17 dipper stickcylinder stroke sensor, 18 bucket cylinder stroke sensor, 19 handrail,25, 25# manipulation device, 25L second manipulation lever, 25Pexcavation mode setting button, 25R first manipulation lever, 26, 26#work implement controller, 28 load sensor, 60 hydraulic cylinder, 64directional control valve, 66 pressure sensor, 200, 200# control system,300 base station.

1. A work vehicle comprising: a vehicular body; a work implement havinga boom pivotable with respect to the vehicular body, a dipper stickpivotable with respect to the boom, and a bucket pivotable with respectto the dipper stick; and a controller that calculates a direction of acutting edge of the bucket and determines a direction in which thecutting edge travels to a side on an open side of the bucket such thatthe calculated direction of the cutting edge of the bucket and thedirection in which the cutting edge travels to the side on the open sideof the bucket form an excavation angle of a predetermined angle, andthat causes an operation of the work implement to be performed in thedirection in which the cutting edge travels.
 2. The work vehicleaccording to claim 1, wherein the controller determines the direction inwhich the cutting edge travels to the side on the open side of thebucket such that the calculated direction of the cutting edge of thebucket and the direction in which the cutting edge travels to the sideon the open side of the bucket form the excavation angle of thepredetermined angle for a predetermined period of time, and thecontroller causes the operation of the work implement to be performed inthe direction in which the cutting edge travels.
 3. The work vehicleaccording to claim 1, further comprising: a first manipulation leveroperated to output a first manipulation command to the controller toadjust an amount of pivoting the bucket with respect to the dipperstick; and a second manipulation lever operated to output a secondmanipulation command to the controller to adjust an amount of moving thebucket for the direction in which the cutting edge travels from thedirection of the cutting edge to the side on the open side of thebucket.
 4. The work vehicle according to claim 3, wherein the controllerdetermines whether to cause the operation of the work implement to beperformed, and when the controller determines that the operation of thework implement is caused to be performed, the controller accepts firstand second manipulation commands from the first and second manipulationlevers.
 5. The work vehicle according to claim 4, wherein the controllerdetermines whether to cause the operation of the work implement to beperformed in accordance with a manipulation instruction of an operator.6. The work vehicle according to claim 5, further comprising a loaddetector that detects a load imposed on the work implement, wherein thecontroller determines whether to cause the operation of the workimplement to be performed according to a result of detection by the loaddetector.
 7. A method for controlling a work vehicle including a workimplement having a boom pivotable with respect to a vehicular body, adipper stick pivotable with respect to the boom, and a bucket pivotablewith respect to the dipper stick, comprising: calculating a direction ofa cutting edge of the bucket; and causing an operation of the workimplement to be performed in a direction in which the cutting edgetravels to a side on an open side of the bucket such that the directionof the cutting edge of the bucket as calculated and the direction inwhich the cutting edge travels to the side on the open side of thebucket form an excavation angle of a predetermined angle.